1. Field of the Invention
The present invention relates generally to an apparatus for forming a thin layer on a semiconductor substrate, and more particularly to a gas injection unit for a chemical vapor deposition apparatus.
2. Description of the Related Art
A chemical vapor deposition apparatus is a device used for depositing a thin layer on a semiconductor substrate placed on a susceptor inside a processing chamber of the chemical vapor deposition apparatus by injecting a processing gas therein through a gas injection unit. The gas injection unit is an apparatus for uniformly injecting the processing gas toward the substrate positioned inside the processing chamber.
When the gas injection unit becomes heated above an ideal processing temperature, it may cause an undesirable chemical reaction inside the gas injection unit and cause the unintended reaction by-product to precipitate and attach to the inner surface of the gas injection unit. To prevent this phenomenon, a cooling unit is employed in order to maintain the gas injection unit at a temperature below the predetermined temperature.
Well known cooling units in the related art proposes installation of a separate coolant pipe inside the gas injection unit to provide cooling. However, there are many problems associated with this known technique in view of that the spaces through which the coolant pipe does not pass may not be cooled smoothly and that it would be very difficult to densely install a cooling water pipe. Further, the cooling water pipe itself has limitations largely due to the fact that the pipe would excessively occupy the space.